The HP21 is a highly accurate hand-held indicator that displays relative humidity, temperature and the dew or frost point. The HP21 is perfect for spot checking HVAC installations, manufacturing and storage areas, and generally for all ambient air measurement within the temperature range of -10 to 60°C (14 to 140 °F). The key features of the HP21 will meet user requirements ranging from the most basic to demanding.



The HP21 indicator has an extensive set of settings and functions that can be configured and enabled by the user with the ROTRONIC HW4 software.

In spite of its sophistication, the HP21 can still be used just as a simple humidity and temperature indicator. Whether you decide or not to take advantage of its full potential, the HP21 will let you have it your way.

Key Features

► Measures relative humidity and temperature

► Calculates the dew or frost point

► Integral probe - cannot be separated from the indicator

► Measuring range: 0 to 100 %RH and -10 to 60 °C (14 to 140 °F)

► Accuracy at 23 °C: ± 1.0 %RH and 0.2 °C

► Temperature unit (°C or °F) selectable from the keypad

► Uses a regular 9V alkaline battery

► LC display with backlight - shows %RH and temperature or calculated parameter and temperature (keypad selection)

► Data recording (%RH and temperature) - up to 2000 value pairs

► Automatic RH sensor test with optional sensor drift correction

► 1-point humidity or temperature adjustment directly from the keypad

► External service connector for full access to the HP21 settings and functions